This invention relates to a marine bollard and more particularly to a marine bollard formed of glass reinforced plastics material, and a method of moulding such a bollard.
Traditionally marine bollards used for mooring ships have been formed from cast iron and steel. A marine bollard of the configuration shown in FIG. 1, which is illustrative of one of the many designs of marine bollards in current use, has been manufactured for many years. One such marine bollard is required to withstand a normal tension on anchorage of up to 20 tons. However, even higher levels, for example loads up to 100 tons, are demanded in some instances. The shipping regulations further require a safety factor of three resulting in this marine bollard needing to withstand a fail safe tension of up to 60 tons. In addition the bollard must have suitable corrosion resistant properties and weatherability properties at its outer surface.
Experience has shown that the cast iron marine bollard whilst being totally acceptable to the shipping authorities for anchoring purposes, does have other drawbacks. In particular, iron for casting marine bollards is a commodity for which bollard manufacturers are subjected to delays in delivery and short term fluctuations in world prices. A more significant economic factor in the pricing of marine bollards concerns the cost of shipping the bollards to their eventual destination. The weight of bollards formed of cast iron means that the shipping cost for exported bollards is a significant factor in the overall price. The weight factor is also a considerable problem in the handling and installation of the bollards. Finally, cast iron is a material which tends to be facture sensitive and requires large scale casting plant to manufacturethe marine bollards, such plant requires considerable capital investment.
It is therefore an object of the present invention to provide a marine bollard which meets the requisite shipping regulations but which is formed of a material which is lighter and thus reduces the shipping costs and the handling problems associated with cast iron bollards. Although the strength requirements of marine bollards initially suggested that plastics material would not be suitable, the present invention stems from feasability studies into the use of plastics materials in the manufacture of marine bollards. As will be subsequently described in the discussion of the preferred embodiments, after initial failures in the design of marine bollards of plastics material, the present invention resulted in the manufacture of a marine bollard having the requisite strength and other properties required.
A method of manufacture has also been developed which is both economic and avoids the use of large scale plant and capital investment on such plant.